JP-2005-307750A describes a conventional fuel injector which includes a cylinder-shaped housing accommodating a coil, a movable core, a stator core, a valve body and an injection port. The stator core and a part of the housing form a magnetic circuit, which is a passage of a magnetic flux generated by energizing the coil, and generate an electromagnetic force. The movable core is suctioned and moved to the stator core by the electromagnetic force along with the valve body, so that the injection port is opened or closed.
However, in an internal combustion engine in which fuel is directly injected into a chamber, when the fuel injector is inserted into an attachment hole placed at a predetermined position of a cylinder head, an outer circumference surface of the housing is surrounded by an inner circumference surface of the attachment hole over the whole circumference.
When a depth of the fuel injector inserted into the attachment hole is large, a coil portion of the housing which accommodates the coil is inserted into the attachment hole. In this case, a portion of the cylinder head which forms the attachment hole becomes a conductor which is ring-shaped and surrounds the coil portion. Since the magnetic circuit is arranged in the coil portion, the magnetic circuit is surrounded by the conductor. An eddy current is generated in the conductor according to a variation in magnetic flux generated in the magnetic circuit. Thus, the electromagnetic force for suctioning the movable core is decreased by an energy loss due to the eddy current generated in the cylinder head.